US3195326A

US3195326A - Photoflash lamp

Info

Publication number: US3195326A
Application number: US208838A
Authority: US
Inventors: John W Shaffer
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1962-07-10
Filing date: 1962-07-10
Publication date: 1965-07-20
Anticipated expiration: 1982-07-20
Also published as: GB993085A

Description

July 20, 1965 J. w. SHAFFER 3,195,326

PHOTOFLASH LAMP Filed July 10, 1962 II II 1 JOHN W. SHAFFER INVENTOR ATTORN Y of their lamps.

United States Patent 3,195,326 PHOTOFLASH LAMP John W. Shatter, Wiiiiamsport, Pan, assignor to Syivania Electric Products line, a corporation of Delaware Filed Juiy It), 1962, Ser. No. 208,838

'4 Claims. (Cl. 67-31) This invention relates to the manufacture of photoflash lamps and more particularly to those photoflash lamps which are provided with means for indicating the presence therein of moisture contamination.

Generally speaking, a photoflash lamp comprises a hermetically sealed envelope containing a source of actinic light, combustion-supporting gas and ignition means. The source of actinic light is usually in the form of shredded foil. The combustion supporting gas is usually oxygen. The ignition means usually comprises an incandescent filament supported by a pair of lead-in wires and beads of fulminating material disposed on said lead-in wires at the junctions of the filament therewith.

In the manufacture of photoflash lamps, the nature and quantity of the foregoing components thereof are regulated and controlled within very close tolerances to maintain a high degree of uniformity from lamp to lamp and thus insure the attainment of uniform light output and timing characteristics for each lamp type, all of which is well known and recognized in the art. It has long been recognized and appreciated by flashlamp manufacturers that from time to time in the manufacture of these lamps, occasionally a lamp envelope is not completely hermetically sealed and contaminating air enters the lamp. Sometimes these leakers are very slow in developing and are not detectable until long after these lamps have been shipped by the manufacturer.

In order to warn the ultimate user of flashlamps against using a leaker, some fiashlamp manufacturers have incorporated a readily visible moisture indicator in each These moisture indicators usually function on a change in color principle, i.e., when a lamp is truly hermetically sealed, the moisture indicator will be of one color but, when exposed to moisture-containing gas such as air, the color of the moisture indicator will change. The most commonly used moisture-sensitive material in fiashlamp manufacture has been cobaltous cobaltic cyanide. When this material is anhydrous, its color is dark blue. In the presence of moisture, it becomes lighter in color and finally changes to pink. Thus a flashlamp user is warned against using a fiashlamp, the moisture indicator of which is pink in color.

Over the years, the use of cobaltous cobaltic cyanide as the moisture-sensitive material of a moisture indicator has been reasonably satisfactory. However, since cobaltous cobaltic cyanide is an insoluble material, it requires a binding agent to hold it in place at the desired locus in the lamp and all of the binding agents used heretofore have exhibited one or more undesirable characteristics which have adversely affected the efliciency of the mois- 7 forms of deterioration are evidenced by the flaking oif of the indicator from the surface to which it has been applied. Other binding substances, which seem to adhere well, tend to be soft and susceptible to displacement to a varying degree by the abrasive action of the shredded foil during its insertion into the lamp envelope. Still others are toxic and their commercial use should be avoided.

Despite these recognized shortcomings, the use 'of 3,i5,32fi Patented July 20, 1965 However, more recently the trend in the fiashlamp industry has been to the use of smaller lamp envelopes having zirconium as the shredded foil combustible and gas fill pressures above atmospheric. This combination of circumstances has resulted in an aggravation of some of the aforementioned deficiencies of the binding agents used heretofore to a point where they are no longer tolerable.

When zirconium is used instead of aluminum as the shredded combustible foil, a significant increase in its abrasive action on the moisture indicator binding agent as compared to aluminum is noted. This condition is further aggravated, indirectly, by the increase in gas fill pressures to superatmospheric because, since the gas and the combustible are usually maintained at or near stoichiometric balance, a substantial increase in the density of the filling of combustible has occurred.

With smaller envelopes, such as less than 10 cc. volume for example, it has been found that an inner protective lacquer coating is not necessary, only an outside coating being needed. This elimination of the inside lacquer coating has posed a substantial problem insofar as the moisture indicator is concerned because now the moisture indicator must be one which adheres well to glass whereas heretofore it was applied to the lacquer coating.

In view of the foregoing, one of the principal objects of this invention is to provide a superiormoisture indi cator for photoflash lamps.

Another object of this invention is to provide a satisfactory moisture indicator for super-atmospheric photoflash lamps which employ zirconium as the shredded combustible foil.

A further object of this invention is to provide a binding agent for a photoflash lamp moisture indicator which does not substantially affect the moisture-sensitive material thereof adversely.

These and other objects, advantages and features are attained, in accordance with the principles of this invention, by using a colloidal magnesium silicate as the binding agent for the moisture indicator in fiashlamps. While I prefer to use colloidal magnesium silicate as the binding agent, other colloidal magnesium silicates, such as for example lithium-magnesium silicate and aluminum-magnesium silicate, may also be employed satisfactorily.

The single figure of the drawing is an elevational view of one type of photoflash lamp provided with a moisture indicator in accordance with the principles of this invention.

In the specific embodiment of the invention illustrated in the accompanying drawing, the photoflash lamp illustrated therein comprises a sealed, light-transmitting envelope 1 within which a quantity of shredded zirconium foil 3 is disposed. The envelope 1 is provided with a filling of combustion-supporting gas, such as oxygen for example, at a pressure of several atmospheres. Preferably, the combustible and the combustion-supporting gas are substantially in stoichiometrio balance. A tungsten filament 5 is disposed within the envelope 1 and is attached to lead-in'wires '7 and 9 which are supported by and extend through insulator button 8. The inner ends of the lead-in

wires

7 and 9 are provided with a quantity of ignition paste 11. through an end of the lamp envelope and are bent into the form, of

stirrups

13 and 15 lying along opposite sides of the press 17, the wires finally re-entering the press 17 some distance away from the points at which they emerge.

The lead-in

wires

7 and 9 extend The

stirrups

13 and 15 define electrical contact members for engagement with electrical contact members of a fiashgun.

In the manufacture of a photofiash lamp of the type just described, the lamp envelope 1 is initially a segment of glass tubing, open at both ends. In the normal sequence of operations, the mount structure, which coma prises filament 5, lead-in

wires

7 and 9 and insulator button 3, is positioned in one of the open ends of the glass tubing and the'press 17 is formed, thereby closing one of the open ends of the tubing. A suitable applicator is then inserted into the remaining open end, of the tubing to provide the inner wall thereof with a moisture indicator spot 19. Thereafter, a charge of combustible, in this instance shredded zirconium foil, is introduced into the remaining open end of the tubing. ,The envelope is then exhausted and provided with :a filling of combustionsupporting gas at several atmospheres pressure and finally the remaining open end is closed by drawing a tip 21. to

thereby define an hermetically sealed envelope.

The photofiash lamp illustrated in the accompanying drawing is of the type identified commercially as an AG-l. The lamp envelope volume of an AG-l is about 1.5 cc.;

the gas pressure is about 4 /2 atmospheres; and the quantity of shredded zirconium foil with which'the lamp is provided is about 20 mgs. per cc. of envelope volume.

On the other hand, one of the other more popular photo-1 flash lamps on the market today is identified commercially as an M2. The lamp envelope volume of an M2 is about 7.5 cc.; the gas pressure is about 1 /4 atmospheres; and the quantity. of the combustible, in this case'shredded aluminum foil, is about 2 mgs. per cc. of envelope volume.

From the foregoing, it is apparent that the. trend is to the use of zirconium in place of aluminum as the combustible,

small envelopes, higher pressures and much greater den-1 sity'of the combustible fill. Since zirconium shreds are much stiifejr, than aluminum shreds of comparable dimen-- sions and since the fill density of zirconium is much greater than thefill density of aluminum, the resulting significant increase in the abrasive action of the combos-- to degradation upon storage, either in the fiuid or dry form, by humidity or microbiological growth. The moisture-indicator spots formed with this material as the binding agent not only adhere quite firmly to the glass envelope but they are also hard enough to effectively resist the abraiding action .of zirconium foil much coarser than that presently used commercially as the combustible material. The thixotropic nature of the wet paste is also advantageous because it prevents running or dripping of the applied spot before drying.

By way of example, I have found that a highly satisfactory moisture indicator may be prepared'by combining a mixture of about 60% colloidal magnesium silicate and about 40% cobaltous cobaltic cyanide by Weight in an appropriate vehicle, such as water or a water-alcohol solution. permntage of colloidal magnesium silicate used may be from about 95% to about 10%, depending upon the desired degree of color inthe resultant indicating spot. The viscosity may be controlled to the desired tible on the moisture indicator has rendered the binding agents used heretofore quite unsatisfactory for large scale commercial production.

During the search for a better binding agent for use in moisture indicator for photoflash-lamps, the following materials were investigated: various natural and synthesis. glues; hydroxymethyl cellulose; polyvinyl pyrollidone; polyvinyl alcohol, and other Water soluble. or permeable polymers; soluble silicates such assodium silicate;

glass dust; colloidal alumina; emulsion-type binders including a urea-formaldehyde resin; and various salts such as the chlorides of barium, zinc, and strontium. Each of these materials exhibited one or more of the previously described deficiencies.

I have found that colloidal magnesium silicates func-.

tion quite satisfactorily as a binding agent for moisture indicators, in photofiash lamps without manifesting any of the undesirable properties which characterize the previously mentioned materials and they adhere quite well to the inner Wall of the glass envelope to which they are applied. When colloidal magnesium silicate is used as they binding agent, the moisture-indicating substance functions at nearly maximum sensitivity and much more elliciently than many of the materials previously used. Some of these binding agents decrease substantially the potential sensitivity ofthe moisture-indicating material either by the formation of a relatively moisture-impermeable film around the particles of the moisture-indicating'material or by the absorption of water by the binding material itself. In either case, this increases the total amount of moisture needed to efiect a detectable color change in the indicator.

In addition, colloidal magnesium silicate is not adversely afiected by any temperatures that can be tolerated by the moisture-indicating material itself; nor is it subject level by adjusting the percentage of solids in the paste.

What I claim is:

1; A photoflashlamp comprising: a light-transmitting envelope; a combustion-supporting gas 'filling in said envelope; a quantity of a filamentary combustible disposed in saidenvelcpe; ignition means disposed in' said envelope in operative relationship with respect to said filamentary combustible; and a moisture indicator disposed in said envelope, said moisture indicator consisting essentially of a mixture'of cobaltous cobaltic cyanide and a colloidal magnesium silicate.

2.?A photoflash lamp comprising: a light-transmitting envelope; a combustion-supporting gas filling in said envelope; a quantity of filamentary zirconium disposed in said envelopeyignition means disposed in said envelope in operative relationship with respect to saidfilamentary zirconium; and a moisture indicator. disposed in said envelope, said moisture indicator consisting essentially ofa mixtureotcobaltous cobaltic cyanide and a colloidal magnesium i silicate.

3. A photofiash lamp comprising: alight-transmitting envelope; a combustion-supporting gas filling in said envelope at a pressure above atmospheric; a quantity of filamentary zirconium disposed in. said envelope; ignition means disposed in said envelope in operative relationship with respect to said filamentary zirconium; and a moisture indicator disposed in said envelope, said moisture indicator consisting essentially of a mixture, of cobaltous cobaltic cyanide and a colloidal magnesium silicate.

4; A phototlash lamp comprising: a light-transmitting envelope; a combustion-supporting gas filling in said envelope at a pressure above atmospheric; a quantity of filamentary zirconium disposed in said envelope, said gas and said filamentary zirconium being substantially in stoichiometric balance; ignition means disposed in said envelope in operative relationship with respect to said filamentary zirconium; anda moisture indicator disposed in said envelope, said moisture indicator consisting essentially of a mixture of cobaltous cobaltic cyanide and a colloidal magnesium silicate.

References titted by theExaminer UNITED STATES PATENTS 1,131,432 3/15 Smith 106-19 2,229,985 1/41 Nowak etal 117-222 2,281,758 5/42 Galat 252-408 2,460,074 1/49 Davis 252-408 2,726,527 12/55 Pipkin 67-31 2,787,149 4/57 Gleim-et a1. 67-31 2,900,349 8/59 Swartz 252-317 2,993,008 7/61 Anderson 67-31 FOREIGN PATENTS 584,463 10/59 Canada.

EDWARD J. l/IICHAEL, Primary Examiner.

FREDERICK L. MATTESON, IR Examiner.

Claims

1. A PHOTOFLASH LAMP COMPRISING: A LIGHT-TRANSMITTING ENVELOPE; A COMBUSTION-SUPPORTING GAS FILLING IN SAID ENVELOPE; A QUANTITY OF FILAMENTARY COMBUSTIBLE DISPOSED IN SAID ENVELOPE; IGNITION MEANS DISPOSED IN SAID ENVELOPE IN OPERATIVE RELATIONSHIP WITH RESPECT TO SAID FILAMENTARY COMBUSTIBLE; AND A MOISTURE INDICATOR DISPOSED IN SAID ENVELOPE, SAID MOISTURE INDICATOR CONSISTING ESSENTIALLY OF A MIXTURE OF COBALTOUS COBALTIC CYANIDE AND A COLLOIDAL MAGNESIUM SILICATE.